1. Field of the Invention
The present invention relates to an original scanning apparatus for scanning an original, and more particularly, to an apparatus provided with a translucent member in an original scanning unit.
2. Description of the Related Art
Conventionally, as modes for reading an image on an original which are employed in an image reading apparatus, the following two modes are well known.
First, a first mode is an original stationary reading mode for setting an original on an original table with a predetermined method and scanning the original set on an original table glass by a movable optical carriage, thereby reading the image on the original in an image reading part.
In addition, a second mode is an original flow reading mode for conveying an original at a predetermined conveying speed and reading an image on the original in a predetermined reading part where a stationary optical carriage unit is disposed.
In the latter original flow reading mode, the optical carriage can be fixed and it is unnecessary to reciprocatingly move the optical carriage every time image is read, as opposed to the former original stationary reading mode. Consequently, the latter original flow reading mode has advantages over the former original stationary reading mode in that an apparatus configuration is not complicated and acceleration of processing is realized.
Moreover, in a copying machine and the like, it has become sufficient to read an original only once even if a plurality of copies are formed from an identical original as a digital processing technique has advanced in recent years. That is, when image information is read once, it is temporarily stored as digital information in a storage medium such as a computer, whereby it has become easy to re-form a necessary number of copied images based on this stored image information. Image reading by the original flow reading mode has an additional advantage in this respect.
Further, from a viewpoint of realizing convenience of operations and acceleration in reading images in the case in which the images are contained in front and rear surfaces of an original, a reading apparatus has also been manufactured which is provided with opposing two optical carriages along a conveying path of an original and is configured to read images contained in respective surfaces of an original by each optical carriage. According to such an apparatus configuration, since images contained in the front and rear surfaces of the original conveyed along a predetermined path can be almost simultaneously flow-read, acceleration of reading processing in duplex copying of the original can be realized.
However, a reading position of an original is always fixed in the conventional image reading apparatus employing the above-mentioned original flow reading mode. Thus, if a dust adheres to the reading part, the dust is inevitably read while an image is read and appears as a streak over the read image.
In general, since a reading part becomes a conveying surface of a moving original, the original is prevented from entering an inside of an optical system by covering the reading part with a transparent member (translucent plate member) such as glass. This reading surface is required to be cleaned periodically in the image reading apparatus of the original moving system due to the reasons described above.
An outer side, which is an original conveying path side, of the reading surface can be easily cleaned because it is exposed to the outside of the image reading apparatus. However, the image reading apparatus must be disassembled in order to remove a dust adhering to its inside on the opposite side of the original conveying path of the reading surface. In particular, in the case of an image reading apparatus having optical systems (reading units) opposing each other above and below an original conveying path in order to read both surfaces of an original, it is highly likely that, in the optical system on the upper side of the original conveying path, dusts in the optical system deposit on the inner side of glass of the reading unit. Thus, stains on the inner surface of the glass are even more serious.